I have been using a Garmin Zumo 660 since 2010. The mount and connections are solid, has a nice 3.5inch out for headphones, can also sync to Bluetooth headsets. Can connect to phone bluetooth and let you answer/make calls via the GPS unit as long as you have a Bluetooth set or an earphone and mic attached to the unit.
Maps are good, plenty of (ahem) ways of getting updated maps. Unit build quality looks solid. Has been through rain and shine and no problem. Has a nice clip out for the unit where I can detach it when stopped at servos etc.
Screen is easy to read under sunlight. Has built in MP3 player. Easy to use wearing gloves. Easy to add POI and plot routes. Has a manual Fuel gauge which is handy. When the fuel gauge detects you are low in fuel, it will show you nearby fuel stops. Has emergency thingy which directs you to nearest SOS services. Has lane view, lane assist, speed cam and live traffic monitoring.
Has a track back feature....you start from some point, go anywhere you want, click track back, and it will guide you back to where you started. Perfect for discovering new routes
Oh and it comes along with a car mount. So I have my normal and topo maps loaded to the GPS. When am not riding, and going camping, I use the same gps in my car and start driving